Limited resources of fossil fuels and increasing amounts of CO2 released from them and causing the greenhouse phenomenon have raised a need for using biomass as a renewable and clean source of energy. Biomass resources can be broadly categorized as agricultural or forestry-based, including secondary sources derived from agro- and wood industries, waste sources and municipal solid wastes. One promising, alternative technology is the production of biofuels i.e. (bio)ethanol from lignocellulosic materials.
Most of the carbohydrates in plants are in the form of lignocellulose, which essentially consists of cellulose, hemicellulose, and lignin. Lignocellulose can be converted into bioethanol and other chemical products via fermentation following hydrolysis to fermentable sugars. In a conventional lignocellulose-to-ethanol process the lignocellulosic material is first pretreated either chemically or physically to make the cellulose fraction more accessible to hydrolysis. The cellulose fraction is then hydrolysed to obtain sugars that can be fermented by yeast or other fermentative organisms into ethanol and distilled to obtain pure ethanol. Lignin is obtained as a main co-product that may be used as a solid fuel.
One barrier of production of biofuels from cellulosic and lignocellulosic biomass is the robustness of the cell walls and the presence of sugar monomers in the form of inaccessible polymers that require a great amount of processing to make sugar monomers available to the micro-organisms that are typically used to produce alcohol by fermentation. Enzymatic hydrolysis is considered to be the most promising technology for converting cellulosic biomass into fermentable sugars. However, enzymatic hydrolysis is used only to a limited amount at industrial scale, and especially when using strongly lignified material such as wood or agricultural waste the technology is not satisfactory. The cost of the enzymatic step is one of the major economic factors of the process. Efforts have been made to improve the efficiency of the enzymatic hydrolysis of the cellulosic material (Badger 2002).
In addition to improving characteristics with respect to individual cellulolytic enzymes it would also be beneficial to improve the enzymatic degradation of cellulosic material by influencing on the activity of cellulases on lignocellulose. Optimization of the components in cellulase mixtures and supplementation of other synergistically acting enzymes would improve hydrolytic efficiency.
WO2005074647 and WO2011035027 disclose isolated polypeptides having cellulolytic enhancing activity and polynucleotides thereof from Thielavia terrestris. WO 2005074656 discloses an isolated polypeptide having cellulolytic enhancing activity and the polynucleotide thereof from Thermoascus aurantiacus. WO2007089290 discloses an isolated polypeptide having cellulolytic enhancing activity and the polynucleotide thereof from Trichoderma reesei. WO2008140749 relates to compositions and methods for degrading or converting a cellulose containing material with a cellulolytic enzyme composition comprising a Trichoderma reesei polypeptide having cellulolytic enhancing activity, and one or more components selected from the group consisting of a CEL7, CEL12 and CEL45 polypeptides having endoglucanase activity or cellobiohydrolase activity. WO2009085868 relates to isolated polypeptides having cellulolytic enhancing activity and polynucleotides thereof from Myceliophthora thermophile. WO2009033071 relates to fungal enzymes from Chrysosporium lucknowense (now reidentified as Myceliophthora thermophile; Visser et al. 2011) and methods for using the enzymes and compositions of such enzymes in a variety of other processes, including washing of clothing, detergent processes, biorefining, deinking and biobleaching of paper and pulp, and treatment of waste streams.
However, there is still a continuous need for new efficient methods of degrading cellulosic substrates, in particular lignocellulosic substrates, and for new cellulase enhancing factors, which can considerably improve the hydrolytic efficiency of cellulase mixtures and also reduce the required enzyme dosage. There is also a need for processes, which are versatile and allow the design of more flexible process configurations. Moreover, there is a need for processes which work not only at moderate temperatures but also at high temperatures, thus increasing the reaction rates and enabling the use of high biomass consistency leading to high sugar and ethanol concentrations. This approach may lead to significant savings in energy and investment costs. The high temperature also decreases the risk of contamination during hydrolysis. The present invention aims to meet at least part of these needs.